The present invention generally relates to apparatus and methods for treatment of airstreams in an Environmental Control System (ECS) to remove particles using an aircraft electrostatic particle separation control system.
ECS of various types and complexity are used in military and civil airplane, helicopter, and spacecraft applications. In aircraft for example, airflow may be circulated to occupied compartments, cargo compartments, and electronic equipment bays. Humid air containing many pollutants such as particulate matter, aerosols, and hydrocarbons may be delivered in a heated condition to the ECS. As the humid air cools, aqueous vapor condenses into liquid. The entrained moisture may be uncomfortable for passengers, unacceptable for air-cooled electronic equipment, may cause windshield fogging, and may cause corrosion to exposed metals. The ECS may include provisions to dehumidify the air supply during cooling operations to provide a comfortable environment for the passengers and crew, where particle separation may be an important function.
One approach to controlling humidity uses electrostatic particle separators. An electrostatic particle separator may extract particles, for example, liquid water from air. Typically, an electrostatic particle separator relies on a high-voltage source to create an electrostatic force around the emitter electrode strong enough to migrate particles away from the electrode and toward the outer walls of the separator. However, when the electric field intensity exceeds the maximum limit that the gas (air) can sustain, a corona discharge will form. The corona discharge may cause a split in the oxygen (O2) molecules. The resulting oxygen atoms (O—), seeking stability, may attach to other oxygen (O2) molecules forming ozone (O3). Ozone is also already normally present in higher concentrations at higher altitude of the Earth's atmosphere. The ozone levels in aircraft cabins have to be controlled under requirements of the Federal Aircraft Regulations (FAR). In some ECSs an ozone-destroying catalytic converter may be used to reduce the ozone levels. However, the converter is typically upstream of the separator and thus ozone produced by the separator may be unaffected.
As can be seen, it may be desirable to control the electrostatic particle separator to generate the least amount of ozone.